"One".relative_identifier(
  "Two",
  key: "Three"
)
"One".relative_identifier(
  "Two",
  key: "Three"
)(
  "Four",
  key: "Five"
)
"One".relative_identifier key: "Two"
"One".relative_identifier unqualified "Two",
                                      key: "Three"
"One".relative_identifier "Two",
                          key: "Three"